feature: Provide custom MetricTags during runtime (#111)

Author: pboos

README.md

@@ -222,6 +222,20 @@ public class ViolationExclusionsExample implements ViolationExclusions {
 }
 ```
 
+### Provide metric tags at runtime
+Sometimes you want to generate your own metric tags based on the violation.
+This can be achieved as demonstrated in the following snippet.
+
+```java
+@Component
+public class MetricTagProviderExample implements MetricTagProvider {
+  @Override
+  public List<MetricTag> getTagsForViolation(OpenApiViolation violation) {
+    return List.of(new MetricTag("rule", violation.getRule()));
+  }
+}
+```
+
 ## Examples
 Run examples with `./gradlew :examples:example-spring-boot-starter-web:bootRun` or `./gradlew :examples:example-spring-boot-starter-webflux:bootRun`.
 

examples/example-spring-boot-starter-web/build.gradle

@@ -9,7 +9,14 @@ plugins {
 dependencies {
     implementation project(':examples:examples-common')
     implementation project(':spring-boot-starter:spring-boot-starter-web')
-    implementation 'org.springframework.boot:spring-boot-starter-web'
+    implementation('org.springframework.boot:spring-boot-starter-web') {
+        exclude group: 'org.springframework.boot', module: 'spring-boot-starter-tomcat'
+        exclude group: 'io.undertow', module: 'undertow-websockets-jsr'
+    }
+
+    implementation 'org.springframework.boot:spring-boot-starter-undertow'
+    implementation 'org.springframework.boot:spring-boot-starter-validation'
+    implementation 'org.hibernate.validator:hibernate-validator'
 
     implementation 'org.springframework.boot:spring-boot-starter-validation'
     implementation(libs.openapi.tools.jacksonDatabindNullable)

openapi-validation-api/src/main/java/com/getyourguide/openapi/validation/api/metrics/MetricTagProvider.java

@@ -0,0 +1,8 @@
+package com.getyourguide.openapi.validation.api.metrics;
+
+import com.getyourguide.openapi.validation.api.model.OpenApiViolation;
+import java.util.List;
+
+public interface MetricTagProvider {
+    List<MetricTag> getTagsForViolation(OpenApiViolation violation);
+}

openapi-validation-api/src/main/java/com/getyourguide/openapi/validation/api/metrics/NullMetricTagProvider.java

@@ -0,0 +1,11 @@
+package com.getyourguide.openapi.validation.api.metrics;
+
+import com.getyourguide.openapi.validation.api.model.OpenApiViolation;
+import java.util.List;
+
+public class NullMetricTagProvider implements MetricTagProvider {
+    @Override
+    public List<MetricTag> getTagsForViolation(OpenApiViolation violation) {
+        return List.of();
+    }
+}

openapi-validation-api/src/main/java/com/getyourguide/openapi/validation/api/metrics/DefaultMetricsReporter.java renamed to openapi-validation-core/src/main/java/com/getyourguide/openapi/validation/core/metrics/DefaultMetricsReporter.java

@@ -1,6 +1,9 @@
-package com.getyourguide.openapi.validation.api.metrics;
+package com.getyourguide.openapi.validation.core.metrics;
 
 import com.getyourguide.openapi.validation.api.log.LogLevel;
+import com.getyourguide.openapi.validation.api.metrics.MetricTag;
+import com.getyourguide.openapi.validation.api.metrics.MetricTagProvider;
+import com.getyourguide.openapi.validation.api.metrics.MetricsReporter;
 import com.getyourguide.openapi.validation.api.metrics.client.MetricsClient;
 import com.getyourguide.openapi.validation.api.model.OpenApiViolation;
 import java.util.ArrayList;
@@ -13,6 +16,7 @@
 public class DefaultMetricsReporter implements MetricsReporter {
 
     private final MetricsClient metricsClient;
+    private final MetricTagProvider metricTagProvider;
     private final Configuration configuration;
 
     @Override
@@ -49,7 +53,8 @@ private MetricTag[] createTagsForViolation(OpenApiViolation violation) {
         violation.getResponseStatus()
             .ifPresent(responseStatus -> tags.add(new MetricTag("status", responseStatus.toString())));
 
-        addAdditionalTags(tags);
+        tags.addAll(getMetricTagsFromConfiguration());
+        tags.addAll(metricTagProvider.getTagsForViolation(violation));
 
         return tags.toArray(MetricTag[]::new);
     }
@@ -64,15 +69,16 @@ private MetricTag[] createTagsForStartup(
         tags.add(new MetricTag("validation_enabled", String.valueOf(isValidationEnabled)));
         tags.add(new MetricTag("sample_rate", String.valueOf(sampleRate)));
         tags.add(new MetricTag("throttling", String.valueOf(validationReportThrottleWaitSeconds)));
-        addAdditionalTags(tags);
+        tags.addAll(getMetricTagsFromConfiguration());
 
         return tags.toArray(MetricTag[]::new);
     }
 
-    private void addAdditionalTags(ArrayList<MetricTag> tags) {
+    private List<MetricTag> getMetricTagsFromConfiguration() {
         if (configuration.getMetricAdditionalTags() != null) {
-            tags.addAll(configuration.getMetricAdditionalTags());
+            return configuration.getMetricAdditionalTags();
         }
+        return List.of();
     }
 
     @Builder

spring-boot-starter/spring-boot-starter-core/src/main/java/com/getyourguide/openapi/validation/autoconfigure/LibraryAutoConfiguration.java

@@ -8,8 +8,9 @@
 import com.getyourguide.openapi.validation.api.log.NoOpLoggerExtension;
 import com.getyourguide.openapi.validation.api.log.OpenApiViolationHandler;
 import com.getyourguide.openapi.validation.api.log.ViolationLogger;
-import com.getyourguide.openapi.validation.api.metrics.DefaultMetricsReporter;
+import com.getyourguide.openapi.validation.api.metrics.MetricTagProvider;
 import com.getyourguide.openapi.validation.api.metrics.MetricsReporter;
+import com.getyourguide.openapi.validation.api.metrics.NullMetricTagProvider;
 import com.getyourguide.openapi.validation.api.metrics.client.MetricsClient;
 import com.getyourguide.openapi.validation.api.metrics.client.NoOpMetricsClient;
 import com.getyourguide.openapi.validation.api.model.ValidatorConfiguration;
@@ -22,6 +23,7 @@
 import com.getyourguide.openapi.validation.core.log.ExclusionsOpenApiViolationHandler;
 import com.getyourguide.openapi.validation.core.log.ThrottlingOpenApiViolationHandler;
 import com.getyourguide.openapi.validation.core.mapper.ValidationReportToOpenApiViolationsMapper;
+import com.getyourguide.openapi.validation.core.metrics.DefaultMetricsReporter;
 import java.util.Optional;
 import java.util.concurrent.LinkedBlockingQueue;
 import java.util.concurrent.ThreadPoolExecutor;
@@ -49,12 +51,16 @@ public ViolationLogger violationLogger(Optional<LoggerExtension> loggerExtension
 
     @Bean
     @ConditionalOnMissingBean
-    public MetricsReporter metricsReporter(Optional<MetricsClient> metricsClient) {
+    public MetricsReporter metricsReporter(
+        Optional<MetricsClient> metricsClient,
+        Optional<MetricTagProvider> metricTagProvider
+    ) {
         var metricName = properties.getValidationReportMetricName() != null
             ? properties.getValidationReportMetricName()
             : DEFAULT_METRIC_NAME;
         return new DefaultMetricsReporter(
             metricsClient.orElseGet(NoOpMetricsClient::new),
+            metricTagProvider.orElseGet(NullMetricTagProvider::new),
             DefaultMetricsReporter.Configuration.builder()
                 .metricName(metricName)
                 .metricAdditionalTags(properties.getValidationReportMetricAdditionalTags())